Ascp FAQs

This topic lists frequently asked questions regarding ascp command:

How do I control the transfer speed?

You can specify a transfer policy that determines how a FASP transfer utilizes the
network resource, and you can specify target and minimum transfer rates
where applicable. With the ascp command, use the following flags to
specify transfer policies that are fixed, fair, high, and low:

Policy

Command template

Fixed

--policy=fixed -l target_rate

Fair

--policy=fair -l target_rate -m min_rate

High

--policy=high -l target_rate -m min_rate

Low

--policy=low -l target_rate -m min_rate

What should I expect in terms of transfer speed? How do I know if something is
"wrong" with the speed?

Aspera's FASP transport has no theoretical throughput limit. Other
than the network capacity, the transfer speed may be limited by rate
settings and resources of the computers. To verify that your system's
FASP transfer can fulfill the maximum bandwidth capacity, prepare
a client machine to connect to this computer, and test the maximum
bandwidth.

Note: This test typically occupies most of a network's bandwidth. Aspera recommends this test
be performed on a dedicated file transfer line or during a time of low
network activity.

On the client machine, start a transfer with fixed bandwidth policy. Start with a lower
transfer rate and increase gradually toward the network bandwidth (for
example, 1m, 5m, 10m, and so on). Monitor the transfer rate and make sure it
fulfills your bandwidth:

$ ascp -l 1m source-file destination

To improve the transfer speed, also consider upgrading the following hardware
components:

What are my choices regarding file overwrites on the destination
computer?

In ascp, you can specify the overwriting rule with the following flags:

--overwrite=always: Always overwrite the file.

--overwrite=never: Never overwrite the file.

--overwrite=diff: Overwrite if file is different from the
source.

--overwrite=older: Overwrite if file is older than the
source.

Note: For --overwrite=diff, if a complete file (that is, no .aspx file)
exists on the destination computer and is the same as the source file, then
the destination file will remain unmodified (no change on
timestamp/attributes either). Otherwise the entire source file will be
retransferred. Note this policy interacts with the resume
policy.